1. Field of the Invention
The invention relates to a self-contained, modular unit and method of using the same for analyzing the mobility, dissipation, and degradation of chemicals and their degradates in the soil.
2. Background Information
With the protection of the environment becoming an ever increasing issue, applying chemicals to the soil is becoming less and less desirable, unless it is first determined that the chemicals will not adversely affect the surrounding soil, crops and plants, as well as the ponds, streams, rivers, and ground water into which the chemicals and their degradates ultimately flow. In fact, new pesticides, herbicides, and other agrochemicals must meet certain guidelines before they may be sold.
Investigating soil characteristics is not new. For example, G. W. Musgrave investigated the loss of precipitation from soil in 1935 which was documented in his paper entitled "A Device for Measuring Precipitation Waters Lost from the Soil As Surface Runoff, Percolation, Evaporation, and Transpiration." Musgrave collected both the leachate and runoff via an intricately developed system of interrelated soil cores and trenches. The soil cores were obtained and removed to a test site which had been built with special piping and trenches to collect the runoff and leachate. Similar tests were run in 1937 by R. S. Stauffer and R. S. Smith. Their tests were documented in their paper entitled, "Variation in Soils with Respect to the Disposition of Natural Precipitation."
The testing of soil characteristics has since evolved past the testing of only loss of precipitation to testing the dissipation of test chemicals. For example, U.S. Pat. No. 5,009,112 (the '112 patent) discloses a method and an apparatus for conducting field dissipation and leachate studies of test chemicals. Like Musgrave and his followers, the '112 patent requires intricate trenches and corresponding soil cores for collecting the leachate. Unlike Musgrave, the method in the '112 patent requires that the cores are left in place and a trench is dug next to the soil core to place the leachate collection means beneath the intact soil core. G. Richter and W. Jury have also documented work on chemical transport through soil in their paper entitled, "A Microlysimeter Field Study of Solute Transport through a Structure Sandy Loam." The Ricter and Jury method included obtaining a soil core, removing it, attaching a funnel to the end to collect the leachate and replacing the soil core. To obtain the leachate, the soil core was removed from the ground. Neither the '112 patent or Ricter and Jury collected the runoff.
With the evolving and ever increasing EPA requirements, a more dependable and complete analysis is required. On-site testing under the conditions which mimic the natural make-up of the soil, the soil and air temperature, the amount of precipitation as well as the actual dosage of the test chemical, is now necessary. The prior art methods discussed above simply do not address all these requirements. Furthermore, less expensive and time consuming procedures are desirable to reduce the cost of testing, even though more factors and parameters are being evaluated which would normally increase the testing expense. For example, the large trenches utilized in most of the prior art methods are expensive because the extensive excavation of soil requires disposal of large amounts of excavated soil. Then, at the end of the experiment, more expense is incurred to refill the trenches. The mere refilling is also undesirable due to potential impact on the surrounding environment due to settling soil and questionable soil stability. Less involved and drastic procedures, such as easily assembled, modular equipment, are also desirable to enable the test to be run in any type of terrain. It would be virtually impossible to use the prior art trench systems if the analysis were required on a mountain or hillside. Finally, due to the increasing use and advantage of radiolabeled test chemicals for experimental purposes to assess mobility and dissipation of chemicals, self-contained equipment is necessary to assure contamination of the surrounding soil and ground water does not occur.
Although each of the prior art methods and apparatus may have met the testing needs at the time, none of the prior art apparatus or test methods addresses each of these issues sufficiently for current day testing. Consequently, a need exists for a self-contained, modular unit and method for testing the mobility, dissipation, and degradation of chemicals and their degradates: in any type of terrain; in conjunction with radiolabeled test chemicals without contamination of the surrounding water and soil by the test chemical; with on-site testing under the conditions which simulate the natural conditions of the soil, the soil and air temperature, the amount of precipitation as well as the actual dosage of the test chemical; and finally, which affords a more dependable and complete analysis by assuring collection and the subsequent testing of the runoff, leachate and soil matrix.